The present invention relates to methyl 2-(2-hydroperoxy-2-propyl)naphthalene-6-carboxylate represented by the formula(I): ##STR2## and a process for producing the same. More in detail, the present invention relates to methyl 2-(2-hydroperoxy-2-propyl) naphthalene-6-carboxylate represented by the formula(I), which is an intermediate compound for producing 2-hydroxynaphthalene- 6-carboxylic acid that is useful as a raw material for producing highpolymeric materials, and to a process for producing methyl 2-(2-hydroperoxy-2-propyl)naphthalene-6-carboxylate at a high purity and in a high yield.
Because of the excellent properties such as high elasticity, high tensile strength and high heat-resistance of the polymeric materials obtained from 2-hydroxynaphthalene-6-carboxylic acid (hereinafter referred to as "acid-6"), acid-6 has attracted the attention as a raw material for fibers and other shaped goods in recent years.
Hitherto, as a process for producing acid-6, the following processes have been known.
(i) A process in which potassium salt of beta-naphthol is reacted with gaseous carbon dioxide at a high temperature and under a pressure (refer to U.S. Pat. Nos. 1,593,816; 4,287,357; 4,345,095; 4,329,494 and 4,345,094),
(ii) A process in which potassium salt of beta-naphthol is reacted with gaseous carbon dioxide in a high-boiling medium at a high temperature and under a pressure(refer to Japanese Patent Applications Laying-Open Nos. 57-95939 and 58-99436) and
(iii) A process in which 6-bromo-2-naphthol is reacted with carbon monoxide in methanol.
However, there are the following demerits in the above-mentioned processes.
Namely, in the processes (i) and (ii), it is necessary to carry out the reaction at a high temperature between 260.degree. and 280.degree. C., and in the process (iii), it is necessary to carry out the reaction under a high pressure of about 70 kg/cm.sup.2. As a result, in these processes a special apparatus is required because of the high reaction temperature or pressure.
In addition, because of the by-production of a large amount of beta-naphthol in the processes (i) and (ii), it is necessary to separate the by-produced beta-naphthol from the reaction product, and as a result the process complicates. Besides, in the processes (i) and (ii), the by-production of 2-hydroxynaphthalene-3-carboxylic acid as one of the isomers of the objective compound (acid-6) is unavoidable and the separation of the by-product from the reaction product is difficult. Such by-production causes a problem of lowering the reaction selectivity.
In addition to the above-mentioned demerits, the yield of acid-6 in the known processes is low, that is, about 26.5%, 45% and 37% in the process (i), (ii) and (iii), respectively and accordingly, the known processes are not adequate as an industrial process.
In consideration of the above-mentioned situations, the present inventors have studied the industrially profitable processes for producing acid-6, and as a result, have found that acid-6 is produced at a high purity in an excellently high yield by subjecting the novel compound, methyl 2-(2-hydroperoxy-2-propyl)naphthalene-6-carboxylate to acid-decomposition and hydrolysis, and based on this finding, the present inventors have succeeded in dissolving the problems of the above-mentioned conventional processes for producing acid-6 and thus attained the present invention.